1. Technical Field
The present invention relates to an arrangement for attenuating vibrations of moving blades of axial turbines, compressors or the like.
2. Background Art
Generally, an axial turbine or compressor has a so-called dove tail structure. Referring to FIG. 9 of the accompanying drawings, illustrated is a major portion of such a type of axial turbine or compressor "e". As depicted, this axial turbine "e" includes a rotor "a", a plurality of grooves "b" formed in an outer surface of the rotor "a", and a plurality of moving blades (or rotor blades) "c" loosely fitted in the grooves "b" respectively. During operation of the turbine or compressor "e", the moving blades "c" vibrate or swing about their pivots (i.e., roots "d") due to gas pressure and/or centrifugal force. In order to suppress the vibrations or swinging movements of the blades "c", conventionally a through opening "f" is formed in each blade "c" near a free end of the blade and a wire "g" is provided to pass through the aligned openings "f". Frictions caused between the wire "g" and the openings "f" due to the vibrations of the blades "c" reduce the vibrations of the blades "c". Ends of the wire "g" are crushed to have enlarged ends (not shown) to prevent the wire "g" from falling off from the through openings "f". The enlarged ends are larger than the openings "f" and made by plastic deformation.
However, the above described conventional arrangement has the following drawbacks:
(1) The wire "g" exits in a gas passage around the rotor "a" so that the wire "g" reduces an area of the gas passage and also raises a resistance of the gas passage. This results in deterioration of aerodynamic performance of the turbine (or compressor) "e"; PA1 (2) A centrifugal force acting on the wire "g" is transmitted to a thin portion of each of the blades "c" so that the blades are likely damaged. In particular, since the opening "f" extends diagonally relative to the thick direction of the associated blade "c", strength of each blade is considerably affected by the opening "f"; and PA1 (3) When removing the blades "c" from the rotor "a" to replace them with new ones, for example, the wire "g" should be cut. Thus, a new wire is always required when reassembling the turbine "e".